Hulk and Mothra. Hulk is all about brute strength and Mothra is a more gentle, yet powerful kaiju. Their personalities contrast. Hulk could initially see Mothra as an enemy but then they could form an alliance. Mothra could use her powers to calm Hulk down when he gets too out of control, and Hulk could protect Mothra from more physical threats like other Titans that might attack her.
Black Widow and Monarch scientists would be an interesting pair. Black Widow is used to dealing with espionage and sneaking around. The Monarch scientists have in - depth knowledge about the Titans. She could help them in a more tactical way, like getting information from shady organizations that might be trying to use the Titans for their own gain. And the scientists could provide her with valuable information about the kaiju to help the Avengers in their fight.
Thor and Godzilla would be an interesting pair. Thor, with his god - like powers and his hammer Mjolnir, could potentially have a showdown with Godzilla. It would be a clash of different kinds of power - Thor's lightning and brute strength against Godzilla's atomic breath and massive size.
In a MCU Monsterverse crossover fanfiction, perhaps the Infinity Stones could be involved. Let's say the Time Stone gets lost and ends up in the Monsterverse. Doctor Strange and some of the other Avengers follow it. There they find that the Titans are somehow connected to the power of the Infinity Stones. They need to work with the Titans to retrieve the Time Stone. Godzilla, being a powerful force of nature, could be the key to accessing the area where the Time Stone is hidden.
Definitely Miles Morales. His different origin story and unique powers compared to MCU's Spider - Man would make for some great interactions. He could show Peter Parker from the MCU new ways to use his spider - powers.
Darth Vader would be an amazing character to include. His imposing presence and incredible power would be a huge threat in the MCU. He could face off against Thor, with their different types of powers creating an epic battle. Another interesting character would be Kylo Ren. His conflicted nature could add an interesting dynamic, especially if he interacted with characters like Captain America who have strong moral compasses.
Inuyasha and Ariel would be an interesting pair. Inuyasha is a rough - around - the - edges half - demon, while Ariel is a curious and adventurous mermaid. Ariel could be fascinated by Inuyasha's otherworldly appearance and his sword, and Inuyasha might be intrigued by Ariel's ability to swim and communicate with sea creatures. They could team up to face a threat that endangers both the sea in the Disney world and Inuyasha's forest in his world.
I think Naruto and Lucifer would be an interesting pair. Naruto's unwavering belief in good and his never - give - up attitude would contrast sharply with Lucifer's more cynical and self - centered nature. Their interactions could be full of tension and also moments of mutual understanding as they learn from each other.
Thor and a Dwarf Lord would be really interesting. Thor with his god - like powers and his hammer Mjolnir could team up with a Dwarf Lord, who is known for his skill in forging and combat. They could exchange stories about their great battles and also work together to create some powerful weapon, perhaps using Asgardian and Dwarven forging techniques.
I think Ian from Shameless and Jude from The Fosters would make an interesting pair. Ian has his own struggles with his identity and relationships, and Jude is also on a journey of self - discovery. They could bond over their shared experiences of not always fitting in with the mainstream. They might start a support group for LGBTQ+ youth in their combined neighborhood.
Mulan and the twins from 'Twitches'. Mulan is a brave and resourceful warrior. The twins have their own unique magical abilities. They could team up in a battle against an evil force that is threatening both their worlds. Mulan could teach the twins some combat skills, and the twins could use their magic to give Mulan an edge in battle, like creating magical distractions or enhancing her weapons.
Hellboy and Wolverine would be a really interesting pair. Wolverine's feral nature and regenerative abilities combined with Hellboy's brute strength and demonic heritage would make for some great action scenes. They could have some really cool banter too, with Wolverine's gruff attitude and Hellboy's dry sense of humor.